1. Field of the Invention
The invention relates to flexible polyurethane foams made from modified polyether polyols and more particularly relates to foams made from polyether polyols modified with epoxy resin-diamine adducts.
2. Description of the Prior Art
Presently, polyether polyols suitable for use in flexible foams are made by the reaction of glycerine with mixtures of alkylene oxides. Persons skilled in the art of making polyols can add alkylene oxides to polyhydric initiators such as glycerine or to an intermediate molecular weight alkylene oxide adduct of the initiator to prepare products in the 20-60 hydroxyl number range. While generally satisfactory, foams prepared from these prior art polyols are not firm enough for many cushioning applications particularly at lower foam densities. Conventional means of producing firmer (higher ILD) foams such as higher functionality initiators, short chain crosslinkers or fillers lead to other deficiencies in foam properties such as closed cells, poor tear and elongation properties and increased foam density. It is, therefore, an object of this invention to increase the functionality of triols by their reaction with epoxy resins-diamine adducts to prepare a new type of polyether polyol which would produce useful flexible foams. The polyols of this invention would also be expected to find application in semiflexible foams and reaction injection molded elastomers.
Other patents disclose reactions involving polyols and epoxy resins. Japanese Patent No. 71-24,255 concerns the reaction of a glycerine-based 3,000 molecular weight triol with 2% bisphenol A epoxy resin to produce foams with increased hardness. A close examination of this patent will show that the epoxy resin is added at only the end of the triol chain.
U.S. Pat. No. 3,012,984 describes how hydroxyl terminated polyesters, epoxy resins and isocyanate terminated prepolymers may be reacted in an inert organic solvent to produce metal primers and coatings. U.S. Pat. No. 3,010,940 discloses how phenol, epoxy resins, polyisocyanates and alphamethylbenzyldimethylamine react to produce various polyurethane coatings. U.S. Pat. No. 3,448,046 describes how polyols containing chlorine are mixed with epoxy resins before reaction with an isocyanate. The free epoxides scavenge the HCl in the polyol and do not contribute to the functionality of the polyol. The reaction of an epoxide with an alcoholic hydroxyl group is set out in U.S. Pat. No. 3,317,609. Further, British Pat. No. 968,102 describes how polyols suitable for polyurethane foams may be prepared from the reaction of a polyol, and an epoxy resin in the presence of an acidic catalyst.
Further prior art polyols include those described in German Offenlegungschrifft No. 2,056,080. This patent describes how epoxy adhesives may be made by the reaction of epoxy resins with 4-mercaptobutanol-blocked urethane prepolymers which are made from toluene diisocyanate and various polyols. German Offenlegungschrifft No. 1,905,696 discloses how polyurethane lattices may be produced by chain-extending a urethane prepolymer by using the reaction product of polyethylene glycols of a molecular weight of about 5,000 to 10,000, and an aromatic diglycidyl ether. The modification of epoxy resins by heating them with added polyalkoxylated disaccharides is described in Belgium Patent No. 785,020.
It is known to modify polyether polyols with epoxy resins alone. For example, U.S. Pat. No. 4,316,991 to Texaco Inc. teaches that polyols modified with epoxy resins of 2,000 to 7,000 molecular weight produce flexible polyurethane foams with higher load bearing properties than unmodified polyols. U.S. Pat. No. 4,309,532, also to Texaco Inc., reveals the modification of rigid amino polyols by their reaction with epoxy resins and alkylene oxides. Polyurethane foams made using these modified polyols are encompassed by U.S. Pat. Nos. 4,373,034 and 4,394,463, respectively.
Other patents disclosing polyethers and polyether polyols from alkylene oxides and compounds having more than one epoxy group include U.S. Pat. Nos. 2,792,354; 3,544,655; 4,113,785 and 4,230,827.